Columella (gastropod)

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An X-ray image of a shell of a marine "triton" snail, Charonia , showing the slightly sinuous line of the central columella, reaching from the top of the image (the apex of the shell) to the bottom (the siphonal canal) Charonia shell.jpg
An X-ray image of a shell of a marine "triton" snail, Charonia , showing the slightly sinuous line of the central columella, reaching from the top of the image (the apex of the shell) to the bottom (the siphonal canal)

The columella (meaning "little column") or (in older texts) pillar is a central anatomical feature of a coiled snail shell, a gastropod shell. The columella is often only clearly visible as a structure when the shell is broken, sliced in half vertically, or viewed as an X-ray image.

Snail mollusc

A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name snail is also used for most of the members of the molluscan class Gastropoda that have a coiled shell that is large enough for the animal to retract completely into. When the word "snail" is used in this most general sense, it includes not just land snails but also numerous species of sea snails and freshwater snails. Gastropods that naturally lack a shell, or have only an internal shell, are mostly called slugs, and land snails that have only a very small shell are often called semi-slugs.

Gastropod shell part of the body of a gastropod or snail

The gastropod shell is part of the body of a gastropod or snail, a kind of mollusc. The shell is an exoskeleton, which protects from predators, mechanical damage, and dehydration, but also serves for muscle attachment and calcium storage. Some gastropods appear shell-less (slugs) but may have a remnant within the mantle, or the shell is reduced such that the body cannot be retracted within (semi-slug). Some snails also possess an operculum that seals the opening of the shell, known as the aperture, which provides further protection. The study of mollusc shells is known as conchology. The biological study of gastropods, and other molluscs in general, is malacology. Shell morphology terms vary by species group. An excellent source for terminology of the gastropod shell is "How to Know the Eastern Land Snails" by John B. Burch now freely available at the Hathi Trust Digital Library.

X-ray form of electromagnetic radiation

X-rays make up X-radiation, a form of electromagnetic radiation. Most X-rays have a wavelength ranging from 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz (3×1016 Hz to 3×1019 Hz) and energies in the range 100 eV to 100 keV. X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays. In many languages, X-radiation is referred to with terms meaning Röntgen radiation, after the German scientist Wilhelm Röntgen who discovered these on November 8, 1895, who usually is credited as its discoverer, and who named it X-radiation to signify an unknown type of radiation. Spelling of X-ray(s) in the English language includes the variants x-ray(s), xray(s), and X ray(s).

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The columella runs from the apex of the shell to the midpoint of the undersurface of the shell, or the tip of the siphonal canal in those shells which have a siphonal canal. If a snail shell is visualized as a cone of shelly material which is wrapped around a central axis, then the columella more or less coincides spatially with the central axis of the shell. In the case of shells that have an umbilicus, the columella is a hollow structure.

Siphonal canal anatomical structure of certain sea snails

The siphonal canal is an anatomical feature of the shells of certain groups of sea snails within the clade Neogastropoda. Some sea marine gastropods have a soft tubular anterior extension of the mantle called a siphon through which water is drawn into the mantle cavity and over the gill and which serves as a chemoreceptor to locate food. In certain groups of carnivorous snails, where the siphon is particularly long, the structure of the shell has been modified in order to house and protect the soft structure of the siphon. Thus the siphonal canal is a semi-tubular extension of the aperture of the shell through which the siphon is extended when the animal is active.

Umbilicus (mollusc)

The umbilicus of a shell is the axially aligned, hollow cone-shaped space within the whorls of a coiled mollusc shell. The term umbilicus is often used in descriptions of gastropod shells, i.e. it is a feature present on the ventral side of many snail shells, including some species of sea snails, land snails, and freshwater snails.

The columella of some groups of gastropod shells can have a number of plications or folds (the columellar fold, plaits or plicae), which are usually visible when looking to the inner lip into the aperture of the shell. These folds can be wide or narrow, prominent or subtle. These features of the columella are often useful in identifying the family, genus, or species of the gastropod.

Aperture (mollusc) The main opening of the shell, where the head-foot part of the body of the animal emerges

The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where the head-foot part of the body of the animal emerges for locomotion, feeding, etc.

Family is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy; it is classified between order and genus. A family may be divided into subfamilies, which are intermediate ranks between the ranks of family and genus. The official family names are Latin in origin; however, popular names are often used: for example, walnut trees and hickory trees belong to the family Juglandaceae, but that family is commonly referred to as being the "walnut family".

A genus is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus.

The surface of the columella is called the columellar wall. The columellar callus is a smooth, calcareous thickening, secreted by the mantle, extending over the columellar area. The columellar lip, the visible part of the columella, is the lower part of the inner lip and is situated near the axis of coiling. A columellar tooth is a raised projection on the inner lip of a columella in the direction of the aperture.

Mantle (mollusc) part of the anatomy of molluscs

The mantle is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself.

Shell of Helix pomatia with a part of shell removed; (4) the columella Czescimuszli shells tags.png
Shell of Helix pomatia with a part of shell removed; (4) the columella

Columellar muscles

The soft parts of the body of the gastropod are held in place in the shell by the columellar muscles. These muscles are attached strongly to the columella itself not just far up in the apex of the shell but also by a long and narrow attachment over the length of a full whorl along the columella. [1] The columellar muscle passes underneath the mantle, greatly thickening the body wall, through the foot and is attached at its other end to inner face of the operculum (if present).

The columellar muscles are contracted when the animal needs to withdraw the foot, head, and other soft parts into the shell for protection from drying out, and from predators. During these contractions the operculum and shell are approximated, and the animal is withdrawn within the latter. [2] The columellar muscles are equally used to bring the soft body out of the shell. During protraction and retraction, the muscle twists, shortens or elongates.

In very large gastropods such as the Queen Conch, Eustrombus gigas, once the columellar muscles are cut with a knife, the soft parts of the animal fall out of the shell easily. Conch fishermen in the Caribbean Sea break a small hole in the spire of the shell, cut the columellar muscles, and harvest the live meat of this species. Often the fishermen dump the empty shell back into the sea again.

Related Research Articles

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<i>Lobatus gigas</i> species of mollusc

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Spire (mollusc)

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Operculum (gastropod) A hard structure which closes the aperture of a gastropod when the animal retreats into the shell

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The clausilium is a calcareous anatomical structure which is found in one group of air-breathing land snails: terrestrial pulmonate gastropod mollusks in the family Clausiliidae, the door snails. The clausilium is one part of the clausilial apparatus.

<i>Melo melo</i> species of mollusc

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<i>Laevistrombus canarium</i> species of mollusc

Laevistrombus canarium is a species of edible sea snail, a marine gastropod mollusc in the family Strombidae. Known from illustrations in books dating from the late 17th century, L. canarium is an Indo-Pacific species occurring from India and Sri Lanka to Melanesia, Australia and southern Japan. The shell of adult individuals is coloured from light yellowish-brown to golden to grey. It has a characteristic inflated body whorl, a flared, thick outer lip, and a shallow stromboid notch. The shell is valued as an ornament, and because it is heavy and compact, it is also often used as a sinker for fishing nets.

The following is a glossary of common English language and scientific terms used in the description of gastropods.

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<i>Solariella charopa</i> species of mollusc

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<i>Isara gabonensis</i> species of mollusc

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Lip (gastropod)

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<i>Pyramidella hastata</i> species of mollusc

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<i>Coelotrochus viridis</i> species of mollusc

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<i>Nassarius fossatus</i> species of mollusc

Nassarius fossatus, the channeled basket snail, is a species of sea snail, a marine gastropod mollusk in the family Nassariidae, the Nassa mud snails or dog whelks. It is native to the west coast of North America where it is found on mudflats on the foreshore and on sand and mud in shallow water.

This outline is provided as an overview of, and organized list of articles relevant to, the subject of gastropods :

<i>Azorilla lottae</i> species of mollusc

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References